An image processing method for removing fog in an image is known, for example as described in non-patent document 1. In this image processing method, an image processing device corrects an input image by dividing the pixel value (R, G, and B) of each pixel of the input image by the pixel value (R, G, and B) of atmospheric light. In addition, the image processing device estimates a density of fog in the corrected input image using the minimum values of R, G, and B in a local region called a dark channel. Then, the image processing device calculates a rough transmittance from the density of fog. Furthermore, the image processing device calculates an accurate transmittance using a method called soft matting. The image processing device removes fog in an image using this transmittance.
Non-patent document 1: K. He, J. Sun and X. Tang, “Single Image Haze Removal Using Dark Channel Prior” CVPR, 2009